Saturation controlled softening/hardening in pure aluminum processed by surface rotation rolling

Abstract Surface rotation rolling (SRR) treatment has been applied to cold-rolled and fully-annealed commercial-purity aluminums to refine the microstructure at the surface region. The treatments result in a strengthening in the as-annealed aluminum but a softening in the cold-rolled one. Although the grain size and dislocation density are different in the initial states, they evolve to the same saturation level after SRR treatment. Comparisons of microstructures produced by SRR, ARB (Accumulative roll-bonding) and SMAT (Surface mechanical attrition treatment) reveal that the saturations of grain size and dislocation density are controlled by strain rate and strain path of the plastic deformation process.